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Suggested Response - Q5

**Discuss the direct influence brewing water has on flavour.

Response:

Water, through the substances dissolved in it, plays a definitive role in beer flavour. It contains many ions that exert direct flavour effects and also exerts indirect effects such as influencing reactions in wort production and fermentation.

  • Beer usually has a pH (or negative log of hydrogen ion concentration) of 4-4.5. Certain conditions may reduce the pH to below that, for example:

    • Using water with low alkalinity and low pH
    • Using yeast that produces a high amount of organic acids
    • Using darker acidic malts (as pH decreases, it will impart an acidic flavour that can become unpleasant)

  • Sodium at low levels imparts sweetness. If sodium exceeds 150 mg/L in beer, it imposes salty, harsh and sour notes.

  • Potassium will also taste salty, but only when above 500 mg/L.

  • Magnesium will contribute astringent and bitter flavours at > 15 mg/L.

  • Iron imparts an unpleasant metallic flavour to beer at very low levels, detectable at 0.05 mg/L in some more delicately flavoured beers.

  • Chloride imparts enhanced mouthfeel and has a smoothing effect on beer texture at 200-300 mg/L. Above that level, it produces an overly full mouthfeel.

  • Sulphate has a mouth-drying or astringent effect on the beer palate and can enhance perceived bitterness at 200-400 mg/L.

  • Poor quality brewing water may also contain other undesirable inorganic or organic compounds originating from:

  • Chlorine that has not been removed, imparts medicinal flavour to beer, especially if combined with organic molecules to form chloromethanes and chlorophenols.

  • Microbial contaminants, some of which can grow during the brewing process up to wort boiling, produce acids such as diacetyl (butter), DMS (sweetcorn), acetaldehyde (green apple), and a range of other undesirable sulphur compounds.

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